This invention relates to adaptive optic (AO) systems and to the manufacture of deformable mirrors (DMs).
Deformable mirrors for reflecting an incoming wave front are generally formed to have a highly precise surface, which surface can be changed with high precision and control. FIGS. 1 and 1A show a known deformable mirror (DM). The mirror includes a thin reflective layer (membrane) overlying the top ends of an array of individual actuators. The bottom ends of the actuators are mounted on a base (substrate). By applying electrical signals to the actuators (which may be of the piezoelectric or electrostatic type), the actuators may be made to expand (extend or elongate) or retract (shrink or get smaller). This causes the portion of the reflective layer corresponding to an activated actuator to move up or down as shown in FIG. 1B. The movement of each actuator enables the mirror surface to move a portion of a wavelength to correctly reflect an incoming wave front. However, the manufacturing and assembly of these DMs is extremely delicate and is subject to many problems. As shown in FIGS. 1 and 1A, the bottom ends of the actuators (e.g., piezo blocks) need to be rigidly held in place on a back plane (substrate) and their top ends need to be properly aligned for the deposition thereon of the mirror membrane (reflective layer). The top end of each actuator is free to change length by pushing the attached mirror membrane upward or pulling it downward. As each actuator is energized, by the application of a signal which varies about a nominal signal value, the corresponding membrane portion is raised or lowered (per the orientation shown in FIGS. 1A and 1B) relative to the value corresponding to the nominal signal value.
These types of devices are expensive to manufacture. They use a thin membrane mirror surface as the active area. They are fragile and are subject to several failure modes when subjected to mechanical forces such as those found during launch conditions.
It is therefore desirable to have a robust device which can be made using standard manufacturing techniques.